The vertebral arteries (VA) play a critical role by supplying nearly one-third of the brain’s blood flow, predominantly contributing to the posterior circulation. These arteries may need to be exposed in a various cranial and cervical procedures and offers access to investigate or treat vascular lesions by endovascular means related to the posterior circulation. Given its complex anatomy, which is subject to numerous variations, and its role in supplying vital brain regions, a thorough understanding of the VA’s anatomy is paramount for any related procedure. In this article, we present a current overview of the VA’s anatomy.

The VAs arise from the subclavian arteries in 94% of instances [1]. Each VA is divided into four segments, designate V1–V4. The first three segments (V1–V3) are extra-cranial, while the final segment, V4, is intradural. Both VAs converge to form the basilar trunk (BT), typically at the pontomedullary junction. The VAs are chiefly responsible for the blood supply for the posterior circulation, contributing to 28% of the overall cerebral blood flow (averaging 201 cc/min) [2], [3]. Asymmetry in the VAs asymmetry is present in 61,4% of cases, with 36,1% showing left dominance and 25,3% demonstrating right dominance [3].

V1 begins from the subclavian artery and extends until its entry into the lowest transverse foramen, generally found at the 6th cervical vertebra. V2 traverses the transverse foramina of the upper six cervical vertebrae and concludes at the entrance of the transverse foramen of C1. V3 progresses through the transverse foramen of C1 and continues until the point where it enters the dura. This is where the V4 begins and continues until it reaches the pontomedullary junction [4], [5] to form the basilar artery.

Based on Barbieri’s 1867 description, some researchers [6], [7], [8], [9] consider that the V2 segment ends at the exit of the transverse foramen of C2 [10]. However, herein we adhere to the classification by Rhoton which draws from the original description by Power in 1860 [11]. This classification designates the end of V2 segment at the entrance of the transverse foramen of C1 [5], [12].